The present invention relates to aluminum-zirconium anti-perspirant systems with complex aluminum buffers. More particularly, the invention is directed to water soluble complexes of zirconium which have a sufficiently high pH to be acceptable in anti-perspirant formulations for application to the human axilla.
It has been known in the art for some time that zirconium salts provide exceptionally effective anti-perspirant properties. Such zirconium compounds have included particularly the acidic zirconium salts, such as zirconium oxy chloride or zirconyl chloride, zirconium hydroxy chloride, and other halide and sulfate substitutes of the salts. However, the zirconium salts are extremely acidic and irritating to the skin. For example, a solution of zirconyl chloride which is effective as an anti-perspirant has a pH of only about 0.8 and a solution of zirconyl hydroxy chloride which is effective as an anti-perspirant has a pH of only about 1.2. As a result, it is necessary to buffer these solution up to a pH which is suitable for application to the human skin, i.e., up to at least about 3 to 5.
A number of prior attempts have been made in the art to buffer solutions of zirconium salts or to form zirconium complexes which take advantage of the effectiveness of zirconium compounds. One early attempt included the development of sodium zirconium lactate for use in cologne-stick type formulations. This lactate complex salt was sufficiently alkaline (pH 8.5), but was ineffective as an anti-perspirant, and was repeatedly implicated in the generation of "zirconium granulomas" in some users.
Other attempts to make use of the acidic zirconium salts involved the buffering of solutions of these salts with urea (see U.S. Pat. No. 2,814,584 to Daley) or water soluble amino acids (see U.S. Pat. Nos. 2,814,585 to Daley, 2,854,382 to Grad, and 3,792,068 to Luedders et al.) or aluminum hydroxy halides (see U.S. Pat. No. 2,906,668 to Beekman).
Recently, various derivatives have been formed incorporating zirconium compounds, including the amine-amide derivatives of U.S. Pat. No. 3,407,254 to Siegal et al., and the polyhydroxy derivatives of U.S. Pat. No. 3,405,153 to Jones and Rubino.
While the above attempts have succeeded in varying degrees in alleviating the acidic characteristics of zirconium salts, an entirely satisfactory zirconium anti-perspirant composition has not been previously found. Thus, it is desired to find a zirconium anti-perspirant composition which effectively makes use of the exceptional anti-perspirant properties of the zirconium, while at the same time offsetting the acidity and other disadvantages of zirconium salts.